The number of people with diabetes worldwide is predicted to increase from 415 million in 2015 to 642 million in 2040. The health care costs of treating the disease account for 12% of the global health expenditure and continue to be a huge economic burden (IDF World Atlas 2015). Type 1 diabetes mellitus (T1DM) constitutes 10-15% of the disease burden and is thought to be triggered by genetic or environmental factors in early childhood, which results in antibody-mediated destruction of insulin producing pancreatic ?-cells causing life-threatening hyperglycemia. In contrast, type 2 diabetes mellitus (T2DM) develops later in life and results from insulin resistance in target tissues and inflammation coupled with an inadequate compensation by the ?-cells. A reduced number of functional ?-cells is a central feature of both T1D and TD2 and an urgent question in islet biology relates to plasticity of ?-cell mass in the long-term goal of developing strategies to treat both forms of the disease. This application is focused on the role of RNA modifications and how they modulate ?-cell proliferation, apoptosis and secretory function. We will use recently developed sequencing approaches to characterize RNA marks (e.g. N6-methyladenosine) in human islets from patients with T2D and in the human beta cell line. We will also examine the effects of knocking down key regulators of methylation including erasers, writers and readers and create genetic mouse models lacking one or more of these regulators in ?-cells to complement the studies in ? cell lines for in vitro and ex vivo experiments. Based on Preliminary Data, we seek to continue our studies with the following Specific Aims: 1. Examine the expression of regulators of m6a methylation, undertake m6A sequencing studies in islets from male and female patients with T2 diabetes and characterize the dynamic RNA methylation changes in the EndoC-bH1 cells in response to metabolites and hormones; 2. Determine the relevance of the methyltransferases in the regulation of ER-mediated events, non-sense mediated decay and secretory responses to hormones; and 3. Interrogate effects of absence of the demethylases on alterations in cell cycle control, DNA damage and chromatin modeling.